Mississippi Republicans and New York Democrats face a similar quandary Tuesday: Hold onto an old political hand and his seniority in Congress, or turn the page to a new era?

Rep. Charles B. Rangel, D-N.Y., and Sen. Thad Cochran, R-Miss., have challenges from their own party that headline this week's bevy of primaries — the last crop of contests until later this summer. Beyond the fate of these two longtime pols, Tuesday's results will test a House GOP program for female candidates in primaries, as well as decide a handful of races in Colorado, Florida and New York.

Here is what to watch for in these contests: 1. Will Cochran be the first senator to lose re-election this cycle? At 76 and after nearly retiring, Cochran is likely running his last Senate race. But he may also be serving his final Senate term, thanks to his failure to secure a majority vote in the primary earlier this month against state Sen. Chris McDaniel. McDaniel prevailed by about 1,400 votes in the first round, and the two Republicans meet again in Tuesday's runoff.

But with support from former Gov. Haley Barbour and his nephews, plus big spending from the U.S. Chamber of Commerce and National Republican Senatorial Committee, most Mississippi operatives aren't counting Cochran out until the votes are counted.

Cochran is a member of the Senate Appropriations Committee, and over the past three weeks his campaign has highlighted exactly how his loss would translate into a hit to the Magnolia State economy. Local tea party activists abhor this kind of federal spending.

But there's another reason this race could be notable for the conservative hardliners: Taking out a longtime appropriator would serve as a sweet follow-up to House Majority Leader Eric Cantor's primary loss in Virginia two weeks ago.

2. Will Rangel survive (again)? Rangel is no stranger to electoral trouble, but several members on Capitol Hill told Roll Call they don't think he will lose his Harlem-based seat. He faces two other Democrats for his party's nomination, including an old foe, state Sen. Adriano Espaillat, who lost to Rangel by 1,086 votes two years ago.

If Rangel survives, many House observers will immediately question whether this is his final term in Congress.

If he loses, Rangel will join the pack of decades-long members leaving Congress this term, including Reps. John D. Dingell, D-Mich., George Miller, D-Calif., and Henry A. Waxman, D-Calif. That trio of longtime Democrats went out on their own terms, but Rangel might not.

3. Is it ladies' night in the House GOP? A House GOP effort to shepherd female candidates through primaries will have two opportunities Tuesday. The program, Project GROW , produced mixed results this spring. But if these two female candidates prevail, Republicans have a reasonable chance at increasing the net number of women in the House Republican Conference next Congress.

In New York’s 21st District, former White House aide Elise Stefanik faces businessman and two-time nominee Matt Doheny. More than $1 million in outside spending shifted the momentum in Stefanik’s favor, and the most recent public poll gave her an 8-point lead. This is a race to replace retiring Democratic Rep. Bill Owens and it is rated Tossup by the Rothenberg Political Report/Roll Call.

4. Will Republicans get their best general election nominees in New York and Colorado? In New York's 1st District, state and national Republicans would prefer state Sen. Lee Zeldin prevail over his Republican rival, wealthy attorney George Demos, in the race to take on Rep. Timothy H. Bishop, a Long Island Democrat. If Zeldin falls short, it's unclear whether national Republican groups will even compete for the seat in the fall. The race is rated Leans Democratic by the Rothenberg Political Report/Roll Call.

Across the country, a Colorado gubernatorial race could prove consequential to federal races on the ballot. State Republicans fear that if former Rep. Tom Tancredo, an immigration firebrand, is the GOP's nominee for governor, he could jeopardize two other competitive races: GOP Rep. Cory Gardner's bid for Senate and Rep. Mike Coffman's re-election race. Colorado polls close at 9 p.m. EST.

5.Who are the future members? In Florida's 19th District special election, businessman Curt Clawson faced his toughest race back in April, when he secured the GOP nod to replace ex-Rep. Trey Radel. The general election in this safely Republican district is all but a formality. Expect to see Clawson sworn into the House in the coming days. Polls close at 7 p.m. EST.

In Colorado's 4th District, Weld County District Attorney Ken Buck, the 2010 Senate GOP nominee, is the favorite to win his party's nomination to succeed Gardner in the House. This is a Safe Republican seat.

Likewise, Nassau County District Attorney Kathleen Rice is expected to win the Democratic primary to succeed retiring Rep. Carolyn McCarthy, a Long Island Democrat in the Empire State's 4th District. The race has potential to become competitive in the fall, but for now is rated Safe Democrat by the Rothenberg Political Report/Roll Call.

6. Does the Oklahoma GOP primary for Senate go to a runoff? Lankford has the momentum in the special primary for the open Senate seat — a product of GOP Sen. Tom Coburn's scheduled resignation at the end of this Congress. Lankford faces former state Speaker T.W. Shannon and a few lesser-known candidates, including former state Sen. Randy Brogdon.

Brogdon is poised to play the spoiler, triggering a runoff by preventing Lankford or Shannon from cresting 50 percent. Lankford could have an advantage in that runoff, as the race to replace him in his House district will also likely go into overtime.